Daily Archives: February 7, 2005

Patient Presentation An 11 month-old male came to clinic with a 1 week history of an itchy red rash. The rash appeared under the child’s arms. It spread to the trunk, neck, arms, hands, legs and feet. He seems to be more bothered at night. The family has tried Calamine lotion, Benadryl®, and hydrocortisone with some relief.
He has been otherwise well and has no recent sick contacts. His social history reveals that he lives at home, does not attend daycare, but does go to weekly playgroups. He has been playing outside on a blanket or in the grass.
The past medical history shows a healthy infant with one ear infection in the past.
His review of systems reveals no fever, upper respiratory infection symptoms, new soaps/lotions/detergents, or applied lawn chemicals.
The pertinent physical exam shows a well appearing infant with normal growth and development. His skin examination shows 1-2 mm red papules with excoriation especially in his axilla, neck, face, arms and hands. His trunk and legs are also less involved. Additionally there are also whitish threadlike lines seen especially around his fingers. In the axilla, there are 2-3 mm red lesions that are slightly nodular. None of the skin is wheapy or cellulitic in appearance.
With the clinical history of pruritis, and evidence of burrows, a diagnosis of scabies was made. The patient was treated with permethrin and parents were instructed on environmental control measures. They were also told that the itching of the scabies may last days to weeks after treatment. The parents felt that the Benadryl did help the itching and would continue to use it for symptomatic relief.

DiscussionScabies results from a mite infection (Sarcoptis scabiei). The female burrows into the skin of the host and tunnels ~2 mm each day laying 2-3 eggs at a time. Fecal pellets are also left behind. Larvae hatch after 3-4 days, reach maturity in 14-17 days, mate, burrow and continue the cycle. Death occurs in 25-30 days.The mite can live 2-3 days outside the human body.

Transmission usually occurs by direct contact or by sharing contaminated linens or clothing. Sexual activity can cause transmission. Scabies often occurs within families. Spread can occur with fomites, but this is less likely. Transmission is unrelated to personal hygiene and infestation occurs in all races and social classes worldwide. Children under 15 years have the highest prevelance.

Patients usually come to attention because of pruritus that is often severe and worse at night. Lesions are small, erythematous papules with obvious excoriation. Burrows are grey/white, threadlike, serpiginous and vary in length. The burrows are often disrupted because of scratching. Papules, wheals, and vesicles can also be seem. Nodules are often seen in covered parts of the body such as the axilla, groin, and genitalia and are a granulomatous response to dead mite antigens and feces. The nodules can persist for weeks to months after effective treatment.
Lesions are commonly found on the sides and webbing of the fingers and toes, flexor surfaces of wrists, extensor surfaces of elbows and kness, axilla, periumbilical areas, waist, and genitalia and buttocks. The scalp and back are generally spared. Children however, are more prone to developing diffuse infections often involving the face and scalp. Secondary infection is common.
Scraping from a non-excoriated papula or burrow may allow visualization of a mite, eggs, or feces under a microscope.

Treatment is usually 100% effective if all environmental control measures are applied along with medication use. All family members and close contact should have treatment at the same time to prevent repeated infections. Topical medication should be massaged thoroughly into the skin over the entire body and generally removed by washing after several hours. A single application should be effective, but often 2 treatments 1 week apart are being recommended.

Permethrin (Elimite®) is a topical agent and is generally considered the most effective. It has decreased absorption than Lindane and therefore less toxicity. Common side effects are mild burning, stinging, rash and redness. Permethrin is more expensive than Lindane.

Lindane (Kwell®) is another topical agent. It is more neurotoxic and therefore should be left on the skin of babies under 1 year of age for shorter time periods. Pregnant women should not use lindane, nor should persons with seizure disorders

Crotamiton (Eurax®) is a topical agent that is associatd with frequent treatment failures.

Ivermectin (Stromectol®) is an oral medication given as a single dose followed by a second dose ~1-2 week later. Cure rate is 70% after the first dose and 95% after the second dose. Scabies treatment is an off-label use of this medication.

Antihistamines are used to treat the pruritis. Treatment of secondary infections with appropriate antibiotics is also important.

Environmental control measures include washing all clothing, bedding and linens in the household in hot water and heating in a drying. Other effective methods include dry cleaning or removing the item from body contact for at least 72 hours. Items that have already been cleaned do not require additional measures.

Figure 9 – Hand with rash caused by scabies from the CDC Laboratory Identification of Parasites of Public Health Concern

Learning Point

Undiagnosed scabies can last for years – hence the term “seven year itch.” Suspect scabies when multiple family members are involved, there is a crescendo in intensity of the problem over 2-3 weeks, or if the pruritis intensifies at night.
The differential diagnosis may include:

Atopic dermatitis / Eczema

Contact dermatitis

Drug reaction

Impetigo

Pitaryiasis Rosea

Seborrheic dermatitis

Pediculosis

Urticaria/ Papular urticaria

Questions for Further Discussion
1. How potentially effective are other possible treatments such as sulfur petrolatum?

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